Does "vent" use the compressor?
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
Does "vent" use the compressor?
The other day it was upper 80's, and I had my wife and little girl in the car and could barely hear them. So I rolled the windows up, turned the temp all the way to cold, and turned on the "vent" (it was the 1 or 2 clicks clockwise from the off position before you get to defrost). I had COLD air! I expected just the coldest air that the fan could find on a hot day with the engine warmed up (aka - just warm air), but it was nearly a/c cold. I had a 2000 Durango that did the same thing, and asked dodgetalk about it, but the guys didn't help out too much. I was wondering if you guys could explain if the vent uses my compressor (and therefore reduces diesel mileage). Thanks in advance.
Last edited by brettdacosta; Apr 21, 2010 at 11:55 AM. Reason: better title
Senior User
Joined: Oct 2008
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Ive heard that the superduty works like a heat pump. so when you turn it cold and on vent you'll probably get colder than expected air. my compressor kicks on and off when i'm using the defrost so its essentially dehydrating the air in the winter. any way that was a reply that i got when i opened my big fat mouth on an a/c question a few months ago. hope it helps.
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
I wish they'd use words instead of those stupid little symbols. Then people could actually communicate.
I don't know what year you have, but I have a 2004.
One click clockwise from off is the little guy with the arrow pointing at his face and feet. I believe this would be called "bi-level".
Two clicks clockwise from off is the little guy with the arrow pointing at his feet. This would be "floor".
Three and four clicks clockwise from off is "defrost/floor" and "defrost"
Once click counter clockwise is the arrow pointing at the little guys face and is "vent"
Two and three clicks counter clockwise is "A/C" and "Max A/C"
My understanding is that the compressor is running in every position except OFF, vent and floor.
I don't know what year you have, but I have a 2004.
One click clockwise from off is the little guy with the arrow pointing at his face and feet. I believe this would be called "bi-level".
Two clicks clockwise from off is the little guy with the arrow pointing at his feet. This would be "floor".
Three and four clicks clockwise from off is "defrost/floor" and "defrost"
Once click counter clockwise is the arrow pointing at the little guys face and is "vent"
Two and three clicks counter clockwise is "A/C" and "Max A/C"
My understanding is that the compressor is running in every position except OFF, vent and floor.
Senior User
Joined: Oct 2008
Posts: 232
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I wish they'd use words instead of those stupid little symbols. Then people could actually communicate.
I don't know what year you have, but I have a 2004.
One click clockwise from off is the little guy with the arrow pointing at his face and feet. I believe this would be called "bi-level".
Two clicks clockwise from off is the little guy with the arrow pointing at his feet. This would be "floor".
Three and four clicks clockwise from off is "defrost/floor" and "defrost"
Once click counter clockwise is the arrow pointing at the little guys face and is "vent"
Two and three clicks counter clockwise is "A/C" and "Max A/C"
My understanding is that the compressor is running in every position except OFF, vent and floor.
I don't know what year you have, but I have a 2004.
One click clockwise from off is the little guy with the arrow pointing at his face and feet. I believe this would be called "bi-level".
Two clicks clockwise from off is the little guy with the arrow pointing at his feet. This would be "floor".
Three and four clicks clockwise from off is "defrost/floor" and "defrost"
Once click counter clockwise is the arrow pointing at the little guys face and is "vent"
Two and three clicks counter clockwise is "A/C" and "Max A/C"
My understanding is that the compressor is running in every position except OFF, vent and floor.
Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
superdutyduck - that makes sense though - defrost must take the moisture out of the air or you will just keep fogging your windows up. I understand it on any defrost section, but I don't get it on the face, the feet, and the face/feet clicks.
dchamberlain - I'll check the feet and the face clicks tonight and let you know if either of them feel cold. I want to say in my Durango they were all cold, but I don't remember. I appreciate your effort - do you have any facts to support your "understanding of the clicks" that you mentioned in your post? I'll check back tomorrow with results.
dchamberlain - I'll check the feet and the face clicks tonight and let you know if either of them feel cold. I want to say in my Durango they were all cold, but I don't remember. I appreciate your effort - do you have any facts to support your "understanding of the clicks" that you mentioned in your post? I'll check back tomorrow with results.
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
This is from the 2004 service manual. It may be different for different years.
SYSTEM AIRFLOW DESCRIPTION - MANUAL CLIMATE CONTROL
Max A/C
When MAX A/C is selected:
When A/C is selected:
When PANEL is selected:
When OFF is selected:
When PANEL/FLOOR is selected:
When FLOOR is selected:
When FLOOR/DEFROST is selected:
When DEFROST is selected:
Max A/C
When MAX A/C is selected:
- The air inlet door vacuum control motor is at full vacuum, closing off outside air and admitting only recirculated air.
- The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum position, directing airflow to the instrument panel A/C registers.
- The heater control valve (if equipped) is at full vacuum, preventing the flow of hot coolant to the heater core. Blended air temperature is not available.
- The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F) .
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. Blended air temperature is not available.
When A/C is selected:
- The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
- The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum position, directing airflow to the instrument panel A/C registers.
- Blended air temperature is available.
- The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F) .
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. Blended air temperature is available.
When PANEL is selected:
- The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
- The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at no vacuum, directing airflow to the instrument panel A/C registers.
- The temperature can be adjusted to heat the air but the air cannot be cooled below the outside temperature.
- The A/C compressor will not operate.
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. Blended air temperature is available but the air cannot be cooled below the interior vehicle temperature.
When OFF is selected:
- The air inlet door vacuum control motor is at full vacuum, closing off outside air from entering the passenger compartment.
- The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum control motor is at full vacuum, closing off airflow to the defrost duct, side window demisters and instrument panel A/C registers.
- The A/C compressor will not operate.
- The blower motor is off.
- The auxiliary blower motor (if equipped) is disabled.
- The coolant control valve (if equipped) is at full vacuum, preventing the flow of warm coolant to the heater core.
When PANEL/FLOOR is selected:
- The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
- The panel/defrost door vacuum control motor is at full vacuum and the panel/floor door vacuum control motor is at partial vacuum, directing airflow to the instrument panel A/C registers and floor duct.
- Blended air temperature is available.
- The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F) .
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. However, the air cannot be cooled unless the A/C is operating on the main climate control system.
When FLOOR is selected:
- The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
- The panel/floor door vacuum control motor is at full vacuum and the panel/defrost door vacuum control motor is at no vacuum, directing airflow to the floor duct.
- The temperature can be adjusted to heat the air, but the air cannot be cooled below the outside temperature.
- The A/C compressor will not operate.
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. However, the air cannot be cooled.
When FLOOR/DEFROST is selected:
- The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
- The panel/defrost door vacuum control motor is at no vacuum and the panel/floor door vacuum control motor is at partial vacuum, directing airflow to the defroster duct, side window demisters and floor duct.
- The temperature can be adjusted to heat or cool the air below the outside temperature.
- The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F) .
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. However, the air cannot be cooled unless the A/C is operating on the main climate control system.
When DEFROST is selected:
- The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
- The panel/defrost door and panel/floor door vacuum control motors are at no vacuum, directing airflow to the defroster duct and side window demisters.
- Blended air temperature is available.
- The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F) .
- The blower motor is on.
- The auxiliary blower motor (if equipped) is enabled. However, the air cannot be cooled unless the A/C is operating on the main climate control system
Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
I have a 1999 7.3L. Anyone got that service manual info? Thanks, so much, dchamberlin. Where would one obtain one of those service manuals, and how much do they usually run? I'm assuming you have an electronic copy?
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Lead Driver
Joined: Sep 2007
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From: Scio, OR
I use ALLDATAdiy.com :: Leading Source of Diagnostic and Repair Information. It is online and you buy either a 1 or 5 year subscription. For the 2004 model year, it seems to be pretty complete. I had a subscription for Dad's '96 and it seemed a lot less complete. If you want to use it, I'd go for a 1 year subscription to start off with and see if you like it.
You can see pricing here...ALLDATAdiy.com :: Buy Your Subscription Today
You can see pricing here...ALLDATAdiy.com :: Buy Your Subscription Today
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Thread Starter
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Tuned
Joined: Apr 2010
Posts: 280
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From: Tullahoma, TN
It appears the 04 info applies to my 99. I tried it last night, and there was definitely a difference in "coldness" between face and face/feet. I couldn't really try the feet alone as I was wearing pants, and it wasn't hot enough to feel warm air if the a/c wasn't on. I just wanted to post the new information. You'd think they're put the face/feet at the one click counterclockwise from the OFF position and keep all the A/C settings on one side. Then you'd have the Face only, Feet only, and then the Defrosts on the other. Oh well - I didn't design it. Thanks again for explaining it.
Cargo Master
Joined: Sep 2007
Posts: 3,049
Likes: 1
I use ALLDATAdiy.com :: Leading Source of Diagnostic and Repair Information. It is online and you buy either a 1 or 5 year subscription. For the 2004 model year, it seems to be pretty complete. I had a subscription for Dad's '96 and it seemed a lot less complete. If you want to use it, I'd go for a 1 year subscription to start off with and see if you like it.
You can see pricing here...ALLDATAdiy.com :: Buy Your Subscription Today
You can see pricing here...ALLDATAdiy.com :: Buy Your Subscription Today
You Keep What You Kill
Joined: Dec 2006
Posts: 4,902
Likes: 2
From: Huntersville, NC
Great find David! The PANEL/FLOOR option is the one that surprised me... I had no idea the compressor could function in that mode. I would "REP" you but FTE tells me the spread the love around... sorry.
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